Highly stable oscillators normally employ crystals as their basic frequency standard. In order to make a variable frequency oscillator with crystal oscillator stability, it is common to employ a plurality of crystal references. This is not only expensive but the switching between one crystal and another does not accommodate itself to rapid frequency changes.
Surface acoustic wave devices are well known as evidenced by the following publications: "Analysis of Interdigital Surface Wave Transducers by Use of an Equivalent Circuit Model" W. R. Smith et al IEEE Transactions on Microwave Theory and Techniques, M.T.T.-17, 856-864 November, 1969; "Design of Surface Wave Delay Lines With Interdigital Transducers" W. R. Smith et al, IEEE Transactions on Microwave Theory and Techniques, M.T.T.-17, 865-873, November 1969; "Impulse Model Design of Acoustic Surface Wave Filters" C. S. Hartman et al IEEE Transactions on Microwave Theory and Techniques, M.T.T.-21, 162-165 April, 1973, "Acoustic Surface Wave Filters" R. H. Tancrell et al proceedings of IEEE, 59, 393-409, March, 1971 and "The Design and Applications of Highly Dispersive Acoustic Surface Wave Filters" H. M. Gerard et al IEEE Transactions on Microwave Theory and Techniques, M.T.T.-21, 176-185, April 1973.
Some work has been done on employing surface acoustic wave devices in oscillators to substitute them for the heretofore used crystals. Much of the work done related to band width considerations of such oscillators and the use of such oscillators as modulators.
It is an object of this invention to provide a highly stable variable frequency oscillator.
It is a further object of this invention to provide a highly stable variable frequency oscillator using a single frequency standard.
It is still a further object of this invention to provide a highly stable variable oscillator which can be rapidly switched from one frequency to the other.